mirror of
https://github.com/xiaoqidun/ofdgo.git
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316 lines
11 KiB
Go
316 lines
11 KiB
Go
// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ofdgo
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import (
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"bytes"
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"crypto"
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"crypto/cipher"
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"crypto/ecdsa"
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"crypto/rand"
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"errors"
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"fmt"
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"io"
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"github.com/emmansun/gmsm/padding"
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"github.com/emmansun/gmsm/sm2"
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"github.com/emmansun/gmsm/sm3"
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"github.com/emmansun/gmsm/sm4"
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"github.com/emmansun/gmsm/smx509"
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)
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// 加密错误可通过errors.Is识别，不包含口令或私钥
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var (
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ErrCredentialsRequired = errors.New("document credentials required")
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ErrInvalidCredentials = errors.New("invalid credentials or damaged encrypted document")
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ErrUnsupportedEncryption = errors.New("unsupported document encryption")
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ErrEncryptionPolicyRequired = errors.New("explicit encryption policy required")
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)
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// Credentials 解密凭据，UserName用于筛选接收者，留空自动匹配，不参与口令派生；证书采用DER编码
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// Password与Decrypter分别用于口令和证书方案，私钥可由外部密码设备持有
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type Credentials struct {
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UserName string
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Password []byte
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Certificate []byte
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Decrypter crypto.Decrypter
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}
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// CryptoProvider 提供GM/T0099的密码运算，不依赖渲染后端
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// SM4采用CBC模式及PKCS#7填充，PasswordKey采用GB/T32918的SM3密钥派生
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// EncryptKey返回SM2密文的ASN.1编码；签名和私钥解密使用crypto.Signer与crypto.Decrypter
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// 提供者不得修改输入字节，返回结果由调用方持有
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type CryptoProvider interface {
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EncryptSM4(key, iv, plaintext []byte) ([]byte, error)
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DecryptSM4(key, iv, ciphertext []byte) ([]byte, error)
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PasswordKey(password []byte) ([]byte, error)
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EncryptKey(certificate, key []byte) ([]byte, error)
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}
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// ReaderOption 阅读器的凭据与密码提供者选项
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type ReaderOption func(*readerOptions)
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// EncryptionRecipient 证书加密接收者，Certificate为SM2公钥证书的DER编码
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type EncryptionRecipient struct {
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UserName string
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UserType string
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Certificate []byte
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}
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// EncryptionOptions 设置GM/T0099加密，口令与证书方案二选一
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// UserName标记口令接收者，不参与口令派生，留空不写入用户名
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// 口令方案应使用足够长的随机口令；标准密钥派生不提供慢速口令哈希
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type EncryptionOptions struct {
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Password []byte
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UserName string
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UserType string
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Recipients []EncryptionRecipient
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Provider CryptoProvider
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}
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// EncryptionInfo 不含敏感凭据的文档加密信息
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// PolicyRequired表示无法继承原策略，保存前需显式设置加密方式
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type EncryptionInfo struct {
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Encrypted bool
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Method string
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Users []string
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Layers int
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PolicyRequired bool
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}
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// readerOptions 保存打开文档时的会话参数
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type readerOptions struct {
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credentials []Credentials
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provider CryptoProvider
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}
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// encryptionState 保存解密来源与可继承的输出策略
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type encryptionState struct {
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info EncryptionInfo
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options *EncryptionOptions
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}
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// GMCryptoProvider 使用纯Go国密实现，可在原生环境和WASM使用
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type GMCryptoProvider struct{}
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// WithCredentials 添加解密凭据，多次调用可解开多层加密
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// 入参: credentials 解密凭据
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// 返回: ReaderOption 阅读选项
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func WithCredentials(credentials Credentials) ReaderOption {
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credentials.Password = bytes.Clone(credentials.Password)
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credentials.Certificate = bytes.Clone(credentials.Certificate)
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return func(options *readerOptions) {
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copy := credentials
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copy.Password = bytes.Clone(credentials.Password)
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copy.Certificate = bytes.Clone(credentials.Certificate)
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options.credentials = append(options.credentials, copy)
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}
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}
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// WithCryptoProvider 设置文档解密的密码提供者
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// 入参: provider 密码提供者，nil使用内置实现
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// 返回: ReaderOption 阅读选项
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func WithCryptoProvider(provider CryptoProvider) ReaderOption {
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return func(options *readerOptions) { options.provider = provider }
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}
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// Encryption 获取文档加密状态，不暴露口令或私钥
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// 返回: EncryptionInfo 加密状态
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func (r *Reader) Encryption() EncryptionInfo {
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return r.encryption.summary()
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}
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// summary 复制不含凭据的加密状态
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// 返回: EncryptionInfo 加密状态
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func (s *encryptionState) summary() EncryptionInfo {
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if s == nil {
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return EncryptionInfo{}
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}
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info := s.info
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info.PolicyRequired = s.options == nil
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info.Users = append([]string(nil), info.Users...)
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return info
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}
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// cloneEncryptionOptions 复制可继承的加密策略，密码提供者保持共享
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// 入参: options 加密策略
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// 返回: *EncryptionOptions 独立策略副本
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func cloneEncryptionOptions(options *EncryptionOptions) *EncryptionOptions {
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if options == nil {
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return nil
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}
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copy := *options
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copy.Password = bytes.Clone(options.Password)
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copy.Recipients = append([]EncryptionRecipient(nil), options.Recipients...)
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for i := range copy.Recipients {
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copy.Recipients[i].Certificate = bytes.Clone(copy.Recipients[i].Certificate)
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}
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return ©
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}
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// Encryption 获取当前保存策略，不暴露口令或私钥
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// 返回: EncryptionInfo 加密状态
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func (e *Editor) Encryption() EncryptionInfo {
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return e.encryption.summary()
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}
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// SetEncryption 设置后续保存的加密策略，nil显式选择明文保存
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// 打开单用户口令或证书加密文档时默认继承原策略；多人口令和多层加密需显式选择输出策略
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// 新的加密密钥与初始向量在每次保存时独立生成，设置不改变文档内容或撤销历史
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// 入参: options 加密策略
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// 返回: error 错误信息
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func (e *Editor) SetEncryption(options *EncryptionOptions) error {
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if options == nil {
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e.encryption = nil
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return nil
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}
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if err := validateEncryptionOptions(*options); err != nil {
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return err
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}
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info := EncryptionInfo{Encrypted: true, Method: "1.1.1", Layers: 1}
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if len(options.Password) != 0 {
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info.Users = []string{options.UserName}
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} else {
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info.Method = "1.1.2"
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for _, recipient := range options.Recipients {
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info.Users = append(info.Users, recipient.UserName)
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}
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}
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e.encryption = &encryptionState{info: info, options: cloneEncryptionOptions(options)}
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return nil
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}
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// writeEncrypted 在全部准备及加密成功后写出结果，取消不产生输出
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// 输出流自身写入失败时调用方仍需丢弃本次输出
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// 入参: writer 输出流
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// 返回: int64 写入字节数, error 错误信息
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func (e *Editor) writeEncrypted(writer io.Writer) (int64, error) {
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if e.encryption.options == nil {
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return 0, ErrEncryptionPolicyRequired
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}
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var plaintext bytes.Buffer
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if _, err := e.writePlaintext(&plaintext); err != nil {
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return 0, err
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}
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defer clear(plaintext.Bytes())
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r, err := NewReader(&Input{reader: bytes.NewReader(plaintext.Bytes()), size: int64(plaintext.Len())})
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if err != nil {
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return 0, err
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}
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defer r.Close()
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parts, err := r.packageData()
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if err != nil {
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return 0, err
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}
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defer func() {
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for _, data := range parts {
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clear(data)
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}
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}()
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data, err := encryptPackageParts(parts, *e.encryption.options, editorProgress(e.OnWriteProgress))
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if err != nil {
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return 0, err
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}
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return io.Copy(writer, bytes.NewReader(data))
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}
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// EncryptSM4 使用SM4-CBC及PKCS#7填充加密
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// 入参: key 密钥, iv 初始向量, plaintext 明文
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// 返回: []byte 密文, error 错误信息
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func (GMCryptoProvider) EncryptSM4(key, iv, plaintext []byte) ([]byte, error) {
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block, err := sm4.NewCipher(key)
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if err != nil {
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return nil, err
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}
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if len(iv) != block.BlockSize() {
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return nil, fmt.Errorf("invalid SM4 IV length")
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}
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out := padding.NewPKCS7Padding(sm4.BlockSize).Pad(bytes.Clone(plaintext))
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cipher.NewCBCEncrypter(block, iv).CryptBlocks(out, out)
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return out, nil
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}
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// DecryptSM4 解密SM4-CBC并校验PKCS#7填充
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// 入参: key 密钥, iv 初始向量, ciphertext 密文
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// 返回: []byte 明文, error 错误信息
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func (GMCryptoProvider) DecryptSM4(key, iv, ciphertext []byte) ([]byte, error) {
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block, err := sm4.NewCipher(key)
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if err != nil {
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return nil, err
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}
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if len(iv) != block.BlockSize() || len(ciphertext) == 0 || len(ciphertext)%block.BlockSize() != 0 {
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return nil, ErrInvalidCredentials
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}
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out := make([]byte, len(ciphertext))
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cipher.NewCBCDecrypter(block, iv).CryptBlocks(out, ciphertext)
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plain, err := padding.NewPKCS7Padding(sm4.BlockSize).ConstantTimeUnpad(out)
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if err != nil {
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clear(out)
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return nil, ErrInvalidCredentials
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}
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return plain, nil
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}
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// PasswordKey 按GB/T32918派生16字节口令密钥
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// 入参: password UTF-8口令
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// 返回: []byte 密钥, error 错误信息
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func (GMCryptoProvider) PasswordKey(password []byte) ([]byte, error) {
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if len(password) == 0 {
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return nil, ErrCredentialsRequired
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}
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return sm3.Kdf(password, sm4.BlockSize), nil
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}
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// EncryptKey 使用SM2公钥证书封装文件密钥
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// 入参: certificate DER证书, key 文件密钥
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// 返回: []byte ASN.1密文, error 错误信息
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func (GMCryptoProvider) EncryptKey(certificate, key []byte) ([]byte, error) {
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cert, err := parseEncryptionCertificate(certificate)
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if err != nil {
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return nil, err
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}
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return sm2.EncryptASN1(rand.Reader, cert.PublicKey.(*ecdsa.PublicKey), key)
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}
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// ParseEncryptionCertificate 解析单张SM2加密证书并返回DER副本
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// 仅检查格式、算法和密钥用途，接收者身份及信任应由调用方确认
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// 入参: certificate PEM或DER证书
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// 返回: []byte DER证书, error 错误信息
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func ParseEncryptionCertificate(certificate []byte) ([]byte, error) {
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cert, err := parseEncryptionCertificate(certificate)
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if err != nil {
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return nil, err
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}
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return bytes.Clone(cert.Raw), nil
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}
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// parseEncryptionCertificate 解析并检查加密证书
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// 入参: certificate PEM或DER证书
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// 返回: *smx509.Certificate 证书, error 错误信息
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func parseEncryptionCertificate(certificate []byte) (*smx509.Certificate, error) {
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cert, err := parseSignatureCertificate(certificate)
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if err != nil {
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return nil, err
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}
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public, ok := cert.PublicKey.(*ecdsa.PublicKey)
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if !ok || !sm2.IsSM2PublicKey(public) {
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return nil, fmt.Errorf("SM2 encryption certificate required")
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}
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if cert.KeyUsage != 0 && cert.KeyUsage&(smx509.KeyUsageKeyEncipherment|smx509.KeyUsageDataEncipherment|smx509.KeyUsageKeyAgreement) == 0 {
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return nil, fmt.Errorf("certificate does not permit encryption")
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}
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return cert, nil
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}
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